Misfire detection through combustion pressure sensor

ABSTRACT

A method is provided for controlling an internal combustion engine. The method includes, but is not limited to the step of measuring in-cylinder pressure of an expansion phase of a combustion cycle of a cylinder of the internal combustion engine and measuring in-cylinder pressure of a compression phase of the combustion cycle of the cylinder of the internal combustion engine. A difference between a polytrophic expansion phase constant of the cylinder of the internal combustion engine and a polytrophic compression phase constant of the cylinder of the internal combustion engine is then determined using the measured expansion phase pressure and the measured compression phase pressure. A misfiring of the cylinder is later detected using the determined difference.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to British Patent Application No.091248.0, filed Jul. 17, 2009, which is incorporated herein by referencein its entirety.

TECHNICAL FIELD

This application relates to firing of internal combustion engine, suchas a diesel engine. In particular, it relates to detection of misfiring.

BACKGROUND

Misfiring detection of an internal combustion engine is often requiredfor improving combustion control. When a cylinder of the engine ismisfiring, un-burnt gas is exhausted from the engine. Consequently,harmful components in the exhaust gas are increased. This also resultsin lowering of engine power output and increasing pollution.Furthermore, if the combustion control is achieved in such a manner asto increase an intake air amount with a high step-response duringinfrequent engine misfiring, an idle speed of the engine can becomeunstable.

Therefore, the misfiring detection is required to determine whenmisfiring occurs so that various combustion conditions, such as ignitiontiming and amount of an intake air, can be controlled advantageously.

SUMMARY

An improved method is provided to determine an occurrence of misfiringbased on in-cylinder pressure data. The method uses the in-cylinderpressure data to determine an occurrence of a misfiring event, on acycle-by-cycle basis. On Board Diagnostics (OBD) or European On BoardDiagnostics (EOBD) can use such misfiring information for engines thatare equipped with in-cylinder pressure sensor and for close-loopcombustion control to reduce misfire occurrence.

The misfiring detection compares polytrophic model for acompression-phase and a polytrophic model for an expansion-phase of acombustion cycle. A misfiring is detected when a difference between thecalculated polytrophic expansion constant and the calculated compressionconstant is smaller than a threshold value. The threshold value can becalibrated, adjusted, or predetermined. In one embodiment, a misfiringis detected when the difference has a negative value.

A misfiring is detected when the calculated polytrophic expansionconstant is smaller than the calculated compression constant. Thiscriterion provides a balance approach that is robust towards noise andmounting error of a crankshaft wheel.

On the one hand, a misfiring detection that is based on only onepressure sample would be too sensitive to noise. On the other hand, amisfiring detection that is based on global parameters, which arerepresentative of all pressure curves, is too sensitive to mountingerrors on crankshaft wheel.

This method has the advantage of enabling diagnosis of engineperformance and it can be used by an On-Board Diagnostic system.

A method is provided for controlling an internal combustion engine. Themethod comprises the step of measuring in-cylinder pressure of anexpansion phase of a combustion cycle of a cylinder of the internalcombustion engine. The internal combustion engine can use pressureignition or spark ignition. The method also includes the step ofmeasuring in-cylinder pressure of a compression phase of the combustioncycle of the cylinder of the internal combustion engine.

A difference between a polytrophic expansion phase constant of thecylinder of the internal combustion engine and a polytrophic compressionphase constant of the cylinder of the internal combustion engine is thendetermined using the measured expansion phase pressure and the measuredcompression phase pressure. After this, a misfiring of the cylinder isdetected using the determined difference. A misfiring can be deemed tooccur when the determined difference is smaller than a threshold valuethat can be calibrated, adjusted, or predetermined. In one aspect of theapplication, the threshold value is zero.

The expansion phase pressure and the compression phase pressure can bemeasured over a pre-determined angular window when the in-cylinderpressure is moderate. The pressure of the expansion phase is measuredafter a major part of combustion has occurred. This has the benefit ofeliminating or reducing influences of the polytrophic expansion phaseconstant and the polytrophic compression phase constant by combustion.

The internal combustion engine can then be controlled using the detectedmisfiring to eliminate the detected misfiring. The timing of fuelinjection and amount of injected fuel can be adjusted to eliminate or toreduce the misfiring. The amount of injected fuel also comprises amountof air to fuel composition and quantity.

An opening and closing of a fuel injector of the cylinder can beadjusted for controlling the internal combustion engine. The opening andclosing of fuel injector can also includes adjustment of input andoutput valves opening and closing timing. In certain case, this alsoincludes adjustment of sparking ignition timing.

An engine control unit is also provided in accordance with an embodimentof the invention. The engine control unit includes a port, a storageunit, and a misfiring detection unit.

Functionally, the port receives an in-cylinder pressure measurement of acylinder of an internal combustion engine. The storage unit stores thereceived in-cylinder pressure measurement of an expansion phase of thecombustion cycle of the cylinder of the internal combustion engine aswell as the in-cylinder pressure measurement of a compression phase ofthe combustion cycle of the cylinder of the internal combustion engine.

The misfiring detection unit determines a difference between apolytrophic expansion phase constant and a polytrophic compression phaseconstant. In particular, the polytrophic expansion phase constant isdetermined using the expansion phase pressure measurement whilst thepolytrophic compression phase constant polytrophic compression phaseconstant is determined using the compression phase pressure measurement.The misfiring detection unit uses the determined difference to detectengine misfiring. A misfiring can be considered detected when thedetermined difference is smaller than a threshold value that can becalibrated, adjusted, or predetermined.

The engine control unit can include a port for receiving engine phaseinformation of the combustion cycle of the cylinder of the internalcombustion engine. This engine phase information is used to determine orto detect its particular engine phase or state for measuring thein-cylinder pressure.

The engine phase information can comprise crankshaft angular positioninformation and camshaft angular position information. Put differently,the engine combustion phase can be determined based on the crankshaftangular position information and camshaft angular position information.In a generic sense, other information can also be used to determine theengine phase information.

The engine control unit can comprise a cylinder control unit forcontrolling a run-time parameter unit of the cylinder of the internalcombustion engine using the detected engine misfiring.

The run-time parameter can comprise a timing of fuel injection. The fuelinjection can further include amount of injected fuel. Further, therun-time parameter unit can comprise a fuel injection unit for releasingfuel into the cylinder.

The engine control unit can include a port for receiving one or moreengine parameters. The engine parameter can be related to enginetemperature information or to engine speed information. The cylindercontrol unit can adjust the run-time parameter using the received engineparameter.

An internal combustion engine and a vehicle are also provided inaccordance with embodiments of the invention. The internal combustionengine includes the above-mentioned engine control unit, one or morecylinders, and a run-time parameter unit. The cylinder comprises anin-cylinder pressure sensor unit for transmitting an in-cylinderpressure measurement to the engine control unit whilst the run-timeparameter unit is provided in the cylinder wherein the run-timeparameter unit is controlled by the engine control unit.

In most implementations, the engine control unit can control the fuelinjection via using a valve of a fuel line of the internal combustionengine. The engine control unit can also control the fuel injection viausing a fuel-rail pressure regulator of the fuel line of the internalcombustion engine.

The vehicle includes the above-mentioned internal combustion engine andone or more wheels that are connected to the internal combustion enginevia a transmission unit. The transmission unit includes gears and one ormore clutches for transmitting rotational forces of the internalcombustion engine to the wheels.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will hereinafter be described in conjunction withthe following drawing figures, wherein like numerals denote likeelements, and

FIG. 1 to FIG. 3 illustrate a first embodiment to determine enginemisfiring using polytrophic constant difference of an engine;

FIG. 1 illustrates a graph of polytrophic constant difference of anengine that is idling or not misfiring and a graph of polytrophicconstants difference of the engine that is misfiring,

FIG. 2 illustrates a graph of polytrophic constant difference of theengine for FIG. 1 with a +3 degree crankshaft wheel error wherein theengine is misfiring;

FIG. 3 illustrates a graph of polytrophic constant difference of theengine for FIG. 1 with a −5 degree crankshaft wheel error wherein theengine is idling;

FIG. 4 and FIG. 5 illustrate a second embodiment to determine enginemisfiring using sum of pressure ratios of the engine;

FIG. 4 illustrates a graph of sum of pressure ratios of the engine forFIG. 1 with +3 degree crankshaft wheel error wherein the engine ismisfiring;

FIG. 5 illustrates a graph of sum of pressure ratios of the engine forFIG. 1 with −4 degree crankshaft wheel error wherein the engine isidling;

FIGS. 6 and 7 illustrate a third embodiment to determine enginemisfiring using IMEP (Indicated Mean Effective Pressure);

FIG. 6 illustrates a graph of IMEP of the engine for FIG. 1 that ismisfiring with +3 degree crankshaft wheel error wherein the engine ismisfiring;

FIG. 7 illustrates a graph of IMEP (Indicated Mean Effective Pressure)of the engine for FIG. 1 with −5 degree crankshaft wheel error whereinthe engine is idling;

FIG. 8 illustrates the engine for FIG. 1 that comprises a plurality ofcylinders;

FIG. 9 illustrates a schematic view of the cylinder of FIG. 8;

FIG. 10 illustrates a valve assembly of the cylinder of FIG. 8 and FIG.9;

FIG. 11 illustrates a method of operating the cylinder of FIG. 8 andFIG. 9,

FIG. 12 illustrates an engine control unit for the cylinder of FIG. 8;

FIG. 13 illustrates a physical layout of a further engine that isequipped with an in-cylinder pressure sensor;

FIG. 14 illustrates a determination of polytrophic compression constantof the engine for FIG. 1; and

FIG. 15 illustrates a determination of polytrophic expansion constant ofthe engine for FIG. 1.

DETAILED DESCRIPTION

The following detailed description is merely exemplary in nature and isnot intended to limit application and uses. Furthermore, there is nointention to be bound by any theory presented in the precedingbackground or summary or the following detailed description.

FIG. 1 to FIG. 7 are analyzes criteria or parameters at engine idleconditions because they represent borderline conditions for misfire. Theidle conditions represent a minimum operating speed of the engine. For apassenger-car engine, the idle speed is customarily between 600 rpm(revolution per minute) and 1,000 rpm.

Small crankshaft-wheel position errors are simulated in the embodimentsof FIG. 1 to FIG. 7 to determine which parameters provide reliableindication of misfiring. On the one hand, positive errors of thecrankshaft would cause some non-detection of misfiring events. For thepositive errors, a Top Dead Centre is recognized too late, wherein theTop Dead Centre refers to a position of a piston wherein the piston isfarthest from its crankshaft. On the other hand, negative errors of thecrankshaft would cause some wrong detection of misfiring events. For thenegative errors, the Top Dead Centre is recognized too early.

FIG. 1 to FIG. 3 show a first embodiment to determine engine misfiringusing a parameter of polytrophic constant difference of a cylinder of anengine. The polytrophic constant is also called a polytropic constant.

The embodiment of FIG. 1 to FIG. 3 is based on the polytrophic modelduring compression and expansion phases. During the compression phase,the polytrophic law is expressed as:

p_(i)V_(i) ^(Kc)=C_(i)  (1)

Where p_(i) represents in-cylinder pressure at a given crankshaft angle,V_(i) represents cylinder volume at the given crankshaft angle, K_(c)represents polytrophic compression exponent, and C_(i) represents thepolytrophic compression constant at the given crankshaft angle.

A polytrophic compression constant (C_compr) is then determined as anaverage of a number of C_(i) values. The number of C_(i) values can beadjusted or be configured. The C_(i) values are calculated for apressure curve of one combustion cycle within a configurable angularwindow 96 in which only compression and no combustion is present, asshown in FIG. 14.

In the similar way, during expansion phase the following polytrophic lawis expressed as:

p_(i)V_(i) ^(Ke)=C_(i)  (2)

Where p_(i) represents in-cylinder pressure at a given crankshaft angle,V_(i) represents cylinder volume at the given crankshaft angle, K_(e)represents polytrophic expansion exponent, and C_(i) represents thepolytrophic compression constant at the given crankshaft angle.

Similar to the polytrophic compression constant, the polytrophicexpansion constant (C_exp) is determined as an average of a configurablenumber of C_(i) values that are calculated for a pressure curve of onecombustion cycle within a configurable angular window 98 in whichexpansion occurs, as depicted in FIG. 15.

Once both polytrophic constants are calculated, they are compared toestimate or to determine if a misfiring cycle has occurred. Inparticular, when a difference between the polytrophic expansion and thecompression constants is smaller than a configurable parameter a misfireevent is considered to have happened, according to the followingformula:

C_exp−C_compr<Threshold  (3)

When combustion is not occurring, the compression and the expansionpolytrophic constants are equal in an ideal case of compression andexpansion. In this case, no heat exchange or air leakage occurs. Inpractice, some thermodynamic losses are present. Hence, the thresholdserves as a configurable parameter to comprehend for thermodynamiclosses for misfire determination.

Put differently, the polytrophic constant difference relates to adifference between a polytrophic expansion constant and a polytrophiccompression constant. In particular, the constants are calculated over alimited angular window for each combustion cycle or each positiveinjection cycle in which pressure level is moderate. The constants arenot calculated during engine over-run, wherein a vehicle of the engineis moving with no throttle and the engine is acting as a brake.

In a special case, the polytrophic constant difference with positivevalues is deemed to indicate that the engine is firing normally whilstthe polytrophic constant difference with negative values is deemed toindicate that the engine is misfiring. In a generic sense, thepolytrophic constant difference that is smaller than a threshold valuecan be deemed to indicate that the engine is misfiring. The thresholdvalue can be calibrated, adjusted, or predetermined.

FIG. 1 shows a graph 1 of polytrophic constant difference of a cylinderof an engine that is idling or is not misfiring and a graph 2 ofpolytrophic constants difference of the cylinder of the engine that ismisfiring. The engine has four cylinders engine. Three of the fourcylinders are experiencing combustion at idle conditions and one of thefour cylinders is experiencing misfire. The graph 1 has data points thathave positive values, which range from about 0.04 to about 0.15. Thus,these data points correctly indicate normal engine firing since thesedata points of graph A has positive values. In contrast, the graph 2 hasdata points that have negative values, which range from about −0.02 toabout −0.05. These data points correctly indicate engine misfiring asthe data points of graph B has negative values.

FIG. 2 depicts a graph 3 of polytrophic constant difference of theengine for FIG. 1 that is misfiring. In this case, the engine has a +3degree crankshaft wheel error. The graph 3 has data points that havenegative values, which range from about −0.002 to about −0.014. Again,these data-points correctly indicate engine misfiring, even though itscrankshaft has a positive wheel error.

FIG. 3 shows a graph 4 of polytrophic constant difference of the enginefor FIG. 1 that is firing normally. The engine, in this case, has a −5degree crankshaft wheel error. The graph 4 has data-points with positivevalues that range from about 0.013 to about 0.04. The data pointsindicate normal combustion cycles, even though the crankshaft has anegative wheel error.

In short, the embodiment of FIG. 1 to FIG. 3 shows that the polytrophicconstant difference parameter has the advantage that it does notrepresent local events that occur occasionally but represent events thatoccur with every engine combustion cycle. Events that occur occasionallyare not useful for detecting engine misfiring.

The polytrophic constant difference parameter does not provide falseresults as shown in FIG. 1 to FIG. 3. Further, the polytrophic constantdifference parameter is robust or is resistant towards noise andcrankshaft-wheel position errors. In other words, noise andcrankshaft-wheel position errors affect the polytrophic constantdifference parameter less than other criteria.

FIG. 4 and FIG. 5 show a second embodiment to determine engine misfiringusing a parameter of a sum of pressure ratios of the cylinder of theengine.

In this embodiment, the sum of pressure ratio P_(R)(θ) along acombustion cycle is defined as:

P _(R)(θ)=P _(cyl)(θ)/P _(mot)(θ)  (4)

Where θ represents crankshaft rotational angle, P_(cyl)(θ) representsfired pressure, which is pressure in combustion chamber when combustionis present, and P_(mot)(θ) represents motored pressure, that is pressurein the combustion chamber with no combustion and with the crankshaftturned by an outside agent.

In addition, for a polytrophic process, P_(mot)(θ) can be defined as:

P _(mot)(θ)=P _(im)(V _(im) /V(θ))^(r)  (5)

Where r represents a real number or polytrophic index, V(θ) representsmotored pressure chamber pressure with respect to a certain crankshaftrotational angle, and V_(im) and P_(im) represent constants.

The sum of pressure ratios with values that are more than apre-determined value are deemed to indicate normal engine firing andvalues that are less than the pre-determined value are deemed toindicate engine misfiring. The pre-determined value as provided here is169.

FIG. 4 shows a graph 5 of sum of pressure ratios of the engine for FIG.1 with +3 degree crankshaft wheel error wherein the engine is misfiring.The graph 5 has data points that have values that range from about 168.0to about 172.8. Hence, many data points of graph E indicate incorrectlynormal combustion.

FIG. 5 depicts a graph 6 of sum of pressure ratios of the engine forFIG. 1 of normal combustion cycles. The engine, as provided here, has −4degree crankshaft wheel error and is idling or is firing normally. Thegraph 6 has data points that have values that range from about 160.5 toabout 168.2. Thus, these data-points indicate incorrectly misfiring.

FIGS. 6 and 7 show a third embodiment to determine engine misfiringusing a parameter of IMEP (Indicated Mean Effective Pressure) of thecylinder of the engine of FIG. 1.

In this embodiment, the IMEP is defined as:

$\begin{matrix}{{IMEP} = {\int_{180}^{- 180}{P\ {V}}}} & (6)\end{matrix}$

Where P represents chamber pressure and V represents chamber volume.

The IMEP with values that are more than a pre-determined value aredeemed to indicate normal engine firing and values that are less thanthe pre-determined value are deemed to indicate engine misfiring. Thepre-determined value, as provided here, is zero.

FIG. 6 shows a graph 7 of IMEP of the engine for FIG. 1 that ismisfiring. The engine, in this case, has +3 degree crankshaft wheelerror. The graph 7 has data points with positive values, which rangefrom about 0.40 to about 0.45. The data points, as based on IMEPcriteria, indicate incorrectly normal engine firing.

FIG. 7 depicts a graph 8 of IMEP of the engine for FIG. 1 that is firingnormally. In this case, the engine has a −5 degree crankshaft wheelerror. The graph 8 has data points with negative values, which rangefrom about −0.40 to about −0.17. These data points, as based on IMEPcriteria, indicate incorrectly engine misfiring.

In short, the embodiment of FIG. 1 to FIG. 3 shows that the parameter ofpolytrophic constant difference criterion is robust against smallcrankshaft wheel errors. This parameter of polytrophic constantdifference does not detect a misfire when the misfire is not present anddoes not detect a misfire when the misfire is present. This is unlikethe embodiments of FIG. 4 to FIG. 7 that show parameter of sum ofpressure ratios and the parameter of IMEP, which does not providereliable indications.

FIG. 8 depicts a compression ignition engine 10 for a vehicle thatcomprises a plurality of combustion cylinders 11, 12, 13, and 15. Theengine 10 is intended for driving or for turning wheels of the vehicleto transport goods or passengers. The cylinders 11, 12, 13, and 15 areused to convert diesel fuel to kinetic energy. The cylinders 11, 12, 13,and 15 are similar to each other and have similar parts.

FIG. 9 shows a schematic view of a cylinder assembly 14 that includesthe cylinder 11 of FIG. 8. The cylinder 11 has a cylinder head 17. Anin-cylinder pressure sensor 16 is installed in the cylinder head 17whilst a piston 18 is slidably disposed in a bore 19 of the cylinder 11.The cylinder head 17, the piston 18, and the bore 19 define or surrounda space that is called a combustion chamber 21.

The piston 18 is connected to a crankshaft 22 via a connecting rod 23. Aposition sensor 50 is attached to the crankshaft 22 whilst an output ofthe crankshaft position sensor 50 is connected to a port 34 of anelectronic engine control unit 31.

An inlet valve 25 is provided at an end of an intake passage 28 of thecylinder head 17 whilst an exhaust valve 26 is provided at an end of anexhaust passage 29 of the cylinder head 17. A fuel injector 30 is fixedto the cylinder head 17 such that an outlet of the fuel injector 30 isdisposed in the combustion chamber 21. The inlet valve 25 and theexhaust valve 26 are placed next to camshafts 47 in a manner as shown inFIG. 10. A position of the camshaft 47 refers to its rotational angle αas shown in FIG. 10.

Referring to the fuel injection 30 of FIG. 9, it is connected to a fueltank 32 via a supply line 33 that is also called a common rail. Disposedin line to the supply line 33 are a filter 35, a pump 36, ahigh-pressure valve 38, and a fuel-rail pressure regulator 40. Thehigh-pressure valve 38 is connected to a port 45 of the engine controlunit 31 whilst the fuel-rail pressure regulator 40 is connected a port46 to the engine control unit 31. A return line 41 also leads from thefuel injector 30 to the tank 32.

Referring to the in-cylinder pressure sensor 16, it includes a sensorhead 42 that is connected to a signal conditioner 43 via two cables 44.The sensor head 42 is located within the combustion chamber 21 whilstthe signal conditioner 43 is located outside of the cylinder 11. Anoutput of the signal conditioner 43 is connected to a port 51 of theengine control unit 31.

In a general sense, although the in-cylinder pressure sensor 16 is shownas being installed directly in the cylinder head 17, it could also beintegrated into the fuel injector 30 or be integrated into a glow plugof the cylinder 11. The glow plug, which is not shown in the figure, canserve to heat the cylinder 11 to ease starting of the engine 10 from anidle state, especially when the engine 10 is cold.

Although the cylinder assembly 14 is intended for pressure ignitionoperation, it a broad sense, can include other parts for spark ignitionoperation. The cylinder assembly 14 can receive fuel or gas for itsoperation.

Functionally, the camshafts 47 are intended for actuating the valves 25and 26. The actuation opens the inlet valve 25 to take in air or gasesinto the combustion chamber 21 or opens the exhaust valve 26 to exhaustthe gases out of the combustion chamber 21. Put differently, thecamshaft 47 modulates supply of the air to the combustion chamber 21 aswell as modulates exhaust of combustion products from the combustionchamber 21.

The in-cylinder pressure sensor 16 measures pressure within thecombustion chamber 21 and it sends the measured pressure readings to theengine control unit 31. The pressure sensor 16 is capable ofwithstanding heat and pressure associated with operation of thecompression ignition engine 10 and is capable of operating in presenceof volatile gases in the combustion chamber 21. Further, the pressuresensor 16 has a high sensitivity and a high signal-to-noise ratio. It isalso immunes to electromagnetic interference and it produces linearreadings within a certain tolerance.

The fuel injector 30 can be in the form of an electro-hydraulic fuelinjector or in the form of a pressure-intensified accumulator-typeinjector. The fuel injector 30 is used to supply or to fill thecombustion chamber 21 with diesel fuel or the like from the tank 32. Thesupply is controlled by the engine control unit 31 via the fuel-railpressure regulator 40 and the high-pressure value 38.

The cylinder 18 is moved by the crankshaft 22 to change volume of thecombustion chamber 21. The volume can be reduced to increase itspressure and temperature to ignite the fuel that is supplied by the fuelinjector 30. The injected fuel ignites or burns at a particulartemperature and pressure. The ignition, which is also called combustion,sends an explosive force onto the cylinder 18 to turn the crankshaft 22.The position or rotational angle of the crankshaft 22 is transmitted tothe engine control unit 31 by the crankshaft position sensor 50.

The engine control unit 31 controls or governs the release of the fuelvia the fuel-rail pressure regulator 40 and the high-pressure valve 38to the combustion chamber 21. The control is based on information fromthe in-cylinder pressure sensor 16 and information from the crankshaftposition sensor 50. The control can also use camshaft positioninformation. This information is used to determine a state or phase of acombustion cycle of the engine 10.

Moreover, the engine control unit 31 can use other additionalinformation of the engine 10 to control the fuel release. The additionalinformation includes temperature, speed, or air intake volume of theengine 10. The control can also relate to timing, duration, or quantityof fuel release.

In a generic sense, the camshaft 47 can be removed from the engine 10 sothat the valves 25 and 26 are not controlled or actuated by the camshaft47 but by an electro-hydraulically means.

FIG. 11 shows graphs that illustrate a method of determining misfiringof the cylinder 11 of the engine 10. The method uses information fromthe in-cylinder pressure sensor 16 and engine cylinder phase or stateinformation.

The cylinder phase information can be derived from crankshaft angularposition information and from camshaft angular position information. Ina broad sense, the engine phase information can be also be derived fromother means. Without engine firing, pressure in the cylinder 11increases always when its volume is decreased whilst its intake valve 25and its exhaust valve 26 are closed.

As shown in FIG. 11, a full engine combustion cycle 54 comprises a firstcrankshaft revolution 55 and a second crankshaft revolution 56. Thefirst crankshaft revolution 55 comprises an intake stroke 58 and acompression stroke 59 whilst the second crankshaft revolution 56comprises an expansion stroke 60 and a compression stroke 61. Thestrokes 58, 59, 60, and 61 are also called a phase or a state. Eachstroke 58, 59, 60, or 61 extends for 180 degrees rotation of thecrankshaft 22.

The crankshaft position signal 63 has a first spike 64 and a secondspike 65 that occurs in both the compression phase 59 and the exhaust61.

Considering the combustion cycle 54, the intake stroke 58 starts at a0-degree point of rotation of the crankshaft 22 and it ends at a180-degree point. During this intake phase 58, the intake valve 25 isopened and the exhaust valve 26 is closed allowing gases or air to fillthe combustion chamber 21. A volume graph 68 shows a volume of thecombustion chamber 21 that increases throughout the intake phase 58 andthat it reaches a first peak 70 at the end of the intake phase 58. Apressure graph 72 that depicts pressure within the combustion chamber 21remains relatively constant throughout the phase.

The compression stroke 59 afterward commences at the 180-degree point ofcrankshaft rotation and ends a 360-degree point of crankshaft rotation.The intake valve 25 and the exhaust valve 26 are closed during thisphase enclosing the gases within the combustion chamber 21. During thisphase, the volume of the cylinder 11 decreases whilst its pressureincreases and reaches at a peak 75 at the end of this compression phase59. Correspondingly, temperature within the combustion chamber 21 alsoincreases. Fuel is injected into the cylinder, as shown at point 48.

In-cylinder pressure is measured during this compression phase 59 todetermine its polytrophic compression constant. The pressure is measuredover a limited angular window of the crankshaft 22.

Then, the expansion stroke 60 starts at the 360-degree point ofcrankshaft rotation and it ends at a 540-degree point of crankshaftrotation. Due to the high temperature and the high pressure within thecombustion chamber 21, the injected fuel ignites during this stroke 60.The intake valve 25 and the exhaust valve 26 are closed allowing theignited fuel to exert a large force on the piston 18 and thereby turningthe crankshaft 22 with the large force. As the crankshaft 22 turns, thevolume of the combustion chamber 21 increases to reach a peak whilst thepressure of the combustion chamber 21 decreases rather quickly.

The in-cylinder pressure is again measured during this expansion phase60 to determine its polytrophic expansion constant. The pressure ismeasured over a limited angular window of the crankshaft 22. Thein-cylinder pressure is measured when the pressure is moderate. Thepressure is moderate in the sense that the pressure is not measuredduring ignition or close to ignition when the in-cylinder pressurereaches a peak. In a general sense, the polytrophic constants are notdetermined or calculated during engine over-run, wherein a vehicle ofthe engine is moving with no throttle and the engine is acting as abrake. Based on the difference between the polytrophic expansionconstant and the compression expansion constant, misfiring of thecylinder is then determined.

Later, the exhaust stroke commences at the 540-degree point and ends a720-degree point. The intake valve 25 is closed and the exhaust valve 26is opened allowing exhaust of the ignited fuel to leave the combustionchamber 21. The volume of the combustion chamber 21 starts to decreasewhilst the pressure within the combustion chamber remains relativelyconstant throughout this stroke 61. The crankshaft signal 63 has thesecond spike 65 at 690-degree point of the exhaust stroke 61.

FIG. 12 shows the engine control unit 31 for the cylinder 11 of theengine 10 of FIG. 8.

The engine control unit 31 comprises a central processing unit 80 thatis connected to a computer memory 82. The central processing unit 80 isconnected to the ports 45, 46, 51, 34, and a port 84.

The central processing unit 80 receives information from the crankshaftposition sensor 50 via the port 34 and in-cylinder pressure measurementsfrom the in-cylinder pressure sensor 16 via the port 51. The pressuremeasurement is used to detect or to determine engine misfiring. Anydetected misfiring is then used to adjust or control fuel injection toeliminate the misfiring. The adjustment can relate to quantity of thefuel injection and duration of the fuel injection.

In a special case, the port 34 receives information from a camshaftposition sensor that is not shown in the figure. Then, the centralprocessing unit 80 stores the crankshaft information, the camshaftinformation and the pressure measurements in the computer memory 82 forlater processing by the central processing unit 80. The processingafterward uses the camshaft position information and the crankshaftposition information to determine engine state or phase.

After this, the central processing unit 80 controls or releases the fuelinjection using the high-pressure valve 38 via the port 45 and using thefuel-rail pressure regulator 40 via the port 46. The central processingunit 80 has electrical current drivers for the control that is not shownin the figure.

FIG. 13 shows a physical layout of a further engine 90 that is equippedwith in-cylinder pressure sensors. The in-cylinder pressure sensors areintegrated with glow plugs 92. In a generic sense, the engine 90 canhave only one or more than one cylinder that is equipped with thepressure sensor.

FIG. 13 also has a graph 94 of in-cylinder pressure with respect tocrankshaft angle. The in-cylinder pressure has a peak of about 47 barwhen the crankshaft angle is about 93 degree.

A controller 93 of the engine 90 receives in-cylinder pressuremeasurements, crankshaft angle information and other information, asillustrated in the FIG. 13.

Although the above description contains much specificity, these shouldnot be construed as limiting the scope of the embodiments but merelyproviding illustration of the foreseeable embodiments. Especially theabove stated advantages of the embodiments should not be construed aslimiting the scope of the embodiments but merely to explain possibleachievements if the described embodiments are put into practice. Thus,the scope of the embodiments should be determined by the claims andtheir equivalents, rather than by the examples given.

While at least one exemplary embodiment has been presented in theforegoing summary and detailed description, it should be appreciatedthat a vast number of variations exist. It should also be appreciatedthat the exemplary embodiment or exemplary embodiments are onlyexamples, and are not intended to limit the scope, applicability, orconfiguration in any way. Rather, the foregoing summary and detaileddescription will provide those skilled in the art with a convenient roadmap for implementing an exemplary embodiment, it being understood thatvarious changes may be made in the function and arrangement of elementsdescribed in an exemplary embodiment without departing from the scope asset forth in the appended claims and their legal equivalents.

1. A method of controlling an internal combustion engine, comprising:measuring in-cylinder pressure of an expansion phase of a combustioncycle of a cylinder of the internal combustion engine; measuringin-cylinder pressure of a compression phase of the combustion cycle ofthe cylinder of the internal combustion engine, determining a differencebetween a polytrophic expansion phase constant and a polytrophiccompression phase constant of the cylinder of the internal combustionengine using the measured expansion phase pressure and the measuredcompression phase pressure; and detecting a misfiring of the cylinderusing the determined difference.
 2. The method of claim 1 wherein themisfiring is deemed to occur when the determined difference is smallerthan a predetermined value.
 3. The method of claim 1, wherein theexpansion phase pressure and the compression phase pressure are measuredover a pre-determined angular window when the in-cylinder pressure ismoderate.
 4. The method of claim 1, further comprising controlling theinternal combustion engine using the detected misfiring to eliminate thedetected misfiring.
 5. The method of claim 4, wherein the controlling ofthe internal combustion engine comprises adjusting opening and closingof a fuel injector of the cylinder.
 6. An engine control unit,comprising: a port for receiving an in-cylinder pressure measurement ofa cylinder of an internal combustion engine; a storage unit for storingthe in-cylinder pressure measurement of an expansion phase and thein-cylinder pressure measurement of a compression phase of a combustioncycle of the cylinder of the internal combustion engine; and a misfiringdetection unit for determining a difference between a polytrophicexpansion phase constant and a polytrophic compression phase constantusing the expansion phase pressure measurement and the compression phasepressure measurement.
 7. The engine control unit of claim 6, wherein theengine control unit further comprises a port for receiving engine phaseinformation of the combustion cycle of the cylinder of the internalcombustion engine.
 8. The engine control unit claim 6, furthercomprising a cylinder control unit for controlling a run-time parameterunit of the cylinder of the internal combustion engine using thedetected engine misfiring.
 9. The engine control unit of claim 8,wherein the run-time parameter comprises a timing of fuel injection. 10.The engine control unit of claim 8, further comprising a port forreceiving at least one engine parameter wherein the at least one engineparameter is used by the cylinder control unit for adjusting therun-time parameter.
 11. An internal combustion engine, comprising: afuel line; a valve of the fuel line; an engine control unit that isadapted to control a fuel injection the valve of the fuel line, theengine control unit comprising: a port for receiving an in-cylinderpressure measurement of a cylinder of an internal combustion engine; astorage unit for storing the in-cylinder pressure measurement of anexpansion phase and the in-cylinder pressure measurement of acompression phase of a combustion cycle of the cylinder of the internalcombustion engine; and a misfiring detection unit for determining adifference between a polytrophic expansion phase constant and apolytrophic compression phase constant using the expansion phasepressure measurement and the compression phase pressure measurement. 12.The internal combustion engine of claim 11, wherein the engine controlunit is adapted to control the fuel injection using a fuel-rail pressureregulator of the fuel line.
 13. The internal combustion engine of claim11, wherein the engine control unit further comprises a port forreceiving engine phase information of the combustion cycle of thecylinder of the internal combustion engine.
 14. The internal combustionengine of claim 11, further comprising a cylinder control unit forcontrolling a run-time parameter unit of the cylinder of the internalcombustion engine using the detected engine misfiring.
 15. The internalcombustion engine of claim 14, wherein the run-time parameter comprisesa timing of fuel injection.
 16. The internal combustion engine of claim14, further comprising a port for receiving at least one engineparameter wherein the at least one engine parameter is used by thecylinder control unit for adjusting the run-time parameter.
 17. Avehicle, comprising: a wheel; a transmission unit; an internalcombustion engine connected to the wheel via the transmission, theinternal combustion engine comprising: a fuel line; a valve of the fuelline; an engine control unit that is adapted to control a fuel injectionthe valve of the fuel line, the engine control unit comprising: a portfor receiving an in-cylinder pressure measurement of a cylinder of aninternal combustion engine; a storage unit for storing the in-cylinderpressure measurement of an expansion phase and the in-cylinder pressuremeasurement of a compression phase of a combustion cycle of the cylinderof the internal combustion engine; and a misfiring detection unit fordetermining a difference between a polytrophic expansion phase constantand a polytrophic compression phase constant using the expansion phasepressure measurement and the compression phase pressure measurement. 18.The vehicle of claim 17, wherein the engine control unit is adapted tocontrol the fuel injection using a fuel-rail pressure regulator of thefuel line.
 19. The vehicle of claim 17, wherein the engine control unitfurther comprises a port for receiving engine phase information of thecombustion cycle of the cylinder of the internal combustion engine. 20.The vehicle of claim 17, further comprising a cylinder control unit forcontrolling a run-time parameter unit of the cylinder of the internalcombustion engine using the detected engine misfiring.
 21. The vehicleof claim 20, wherein the run-time parameter comprises a timing of fuelinjection.
 22. The vehicle of claim 20, further comprising a port forreceiving at least one engine parameter wherein the at least one engineparameter is used by the cylinder control unit for adjusting therun-time parameter.